jhrotko commented on code in PR #1136:
URL: https://github.com/apache/arrow-java/pull/1136#discussion_r3200233619
##########
vector/src/main/java/org/apache/arrow/vector/complex/impl/UnionLargeListReader.java:
##########
@@ -53,9 +53,24 @@ public boolean isSet() {
@Override
public void setPosition(int index) {
+ int valueCount = vector.getValueCount();
+ if (UnionListReaderBoundsChecker.isEmptyVectorPosition(index, valueCount))
{
+ setEmptyPosition(index);
+ return;
+ }
+
+ UnionListReaderBoundsChecker.checkIndex(index, valueCount);
+ UnionListReaderBoundsChecker.checkOffsetBuffer(vector.getOffsetBuffer(),
index, OFFSET_WIDTH);
+
+ super.setPosition(index);
+ currentOffset = vector.getElementStartIndex(index) - 1;
+ maxOffset = vector.getElementEndIndex(index);
+ }
+
+ private void setEmptyPosition(int index) {
super.setPosition(index);
- currentOffset = vector.getOffsetBuffer().getLong((long) index *
OFFSET_WIDTH) - 1;
- maxOffset = vector.getOffsetBuffer().getLong(((long) index + 1L) *
OFFSET_WIDTH);
+ currentOffset = 0;
Review Comment:
`isEmptyVectorPosition` conflates two things: "the vector is empty"
(`valueCount == 0`) and "index is `0`." If `valueCount == 0`, why is `index ==
0` special at all? Any access on an empty vector should throw, OR the guard
should be just `valueCount == 0` (allowing `setPosition(n)` on empty vectors to
succeed for any `n`). The current behavior silently succeeds only for index `0`
and throws for any other index on an empty vector, which is asymmetric and
surprising.
##########
vector/src/main/java/org/apache/arrow/vector/complex/impl/UnionListReader.java:
##########
@@ -52,14 +52,24 @@ public boolean isSet() {
@Override
public void setPosition(int index) {
- super.setPosition(index);
- if (vector.getOffsetBuffer().capacity() == 0) {
- currentOffset = 0;
- maxOffset = 0;
- } else {
- currentOffset = vector.getOffsetBuffer().getInt(index * (long)
OFFSET_WIDTH) - 1;
- maxOffset = vector.getOffsetBuffer().getInt((index + 1) * (long)
OFFSET_WIDTH);
+ int valueCount = vector.getValueCount();
+ if (UnionListReaderBoundsChecker.isEmptyVectorPosition(index, valueCount))
{
+ setEmptyPosition(index);
+ return;
}
+
+ UnionListReaderBoundsChecker.checkIndex(index, valueCount);
Review Comment:
you could further move both these methods (`setPosition` and `setEmpty` to
he common packcage as well and make a single call here)
##########
vector/src/main/java/org/apache/arrow/vector/complex/impl/UnionListReaderBoundsChecker.java:
##########
@@ -0,0 +1,47 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.arrow.vector.complex.impl;
+
+import org.apache.arrow.memory.ArrowBuf;
+
+/** Shared position validation for union list readers backed by offset
buffers. */
+final class UnionListReaderBoundsChecker {
+
+ private UnionListReaderBoundsChecker() {}
+
+ static boolean isEmptyVectorPosition(int index, int valueCount) {
Review Comment:
The method name implies it checks whether a specific position holds an empty
list. It actually checks whether the vector itself is empty (`valueCount ==
0`). A name like `isEmptyVector` or `shouldBypassEmptyVector` would be clearer
##########
vector/src/test/java/org/apache/arrow/vector/ipc/TestRoundTrip.java:
##########
@@ -326,6 +329,82 @@ public void testMetadata(String name, IpcOption
writeOption) throws Exception {
}
}
+ @ParameterizedTest(name = "options = {0}")
+ @MethodSource("getWriteOption")
+ public void testEmptyUnionListReadersAfterIpc(String name, IpcOption
writeOption)
+ throws Exception {
+ Field structField =
+ new Field(
+ "struct",
+ FieldType.nullable(ArrowType.Struct.INSTANCE),
+ Collections2.asImmutableList(
+ listField("list", ArrowType.List.INSTANCE),
+ listField("largeList", ArrowType.LargeList.INSTANCE),
+ mapField("map")));
+ Schema schema = new Schema(Collections2.asImmutableList(structField));
+
+ try (final BufferAllocator originalVectorAllocator =
+ allocator.newChildAllocator("original vectors", 0,
allocator.getLimit());
+ final StructVector vector = (StructVector)
structField.createVector(originalVectorAllocator)) {
+ vector.allocateNewSafe();
+ vector.setValueCount(0);
+
+ List<FieldVector> vectors = Collections2.asImmutableList(vector);
+ VectorSchemaRoot root = new VectorSchemaRoot(schema, vectors, 0);
+ roundTrip(
+ name,
+ writeOption,
+ root,
+ /* dictionaryProvider */ null,
+ TestRoundTrip::writeSingleBatch,
+ validateFileBatches(new int[] {0},
this::validateEmptyUnionListReaders),
+ validateStreamBatches(new int[] {0},
this::validateEmptyUnionListReaders));
+ }
+ }
+
+ private Field listField(String name, ArrowType type) {
+ return new Field(
+ name,
+ FieldType.nullable(type),
+ Collections2.asImmutableList(
+ new Field(
+ BaseRepeatedValueVector.DATA_VECTOR_NAME,
+ FieldType.nullable(new ArrowType.Int(32, true)),
+ null)));
+ }
+
+ private Field mapField(String name) {
+ Field keyField =
+ new Field(MapVector.KEY_NAME, FieldType.notNullable(new
ArrowType.Int(32, true)), null);
+ Field valueField =
+ new Field(MapVector.VALUE_NAME, FieldType.nullable(new
ArrowType.Int(32, true)), null);
+ Field entriesField =
+ new Field(
+ MapVector.DATA_VECTOR_NAME,
+ FieldType.notNullable(ArrowType.Struct.INSTANCE),
+ Collections2.asImmutableList(keyField, valueField));
+
+ return new Field(
+ name,
+ FieldType.nullable(new ArrowType.Map(false)),
+ Collections2.asImmutableList(entriesField));
+ }
+
+ private void validateEmptyUnionListReaders(int expectedCount,
VectorSchemaRoot root) {
+ assertEquals(0, expectedCount);
+
+ FieldReader structReader = root.getVector("struct").getReader();
+ assertEmptyUnionListReader(structReader.reader("list"));
+ assertEmptyUnionListReader(structReader.reader("largeList"));
+ assertEmptyUnionListReader(structReader.reader("map"));
+ }
+
+ private void assertEmptyUnionListReader(FieldReader reader) {
Review Comment:
`assertEmptyUnionListReader` never calls `reader.setPosition(0)`, which is
the exact scenario that was broken.
The test should include `reader.setPosition(0)` followed by `assertEquals(0,
reader.size())` and `assertFalse(reader.next())`, otherwise you're not actually
verifying the bug is fixed, just that the initial field defaults happen to be 0.
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